Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – For cleaning a specific substrate or removing a specific...
Reexamination Certificate
1999-11-18
2002-04-09
Ogden, Necholus (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
For cleaning a specific substrate or removing a specific...
C510S377000, C510S446000, C510S421000, C510S424000, C510S427000, C510S507000, C510S509000
Reexamination Certificate
active
06369015
ABSTRACT:
TECHNICAL FIELD
The present invention relates to particulate laundry detergent compositions containing anionic surfactants in the form of granules having a low to moderate bulk density and excellent dissolution properties. The compositions are especially suitable for use in low-temperature and/or low agitation wash processes, more particularly for washing by hand.
BACKGROUND AND PRIOR ART
Laundry detergent powders containing high levels of anionic surfactants are widely known and used for washing fabrics by hand, the high levels being desirable in order to provide effective soil removal and good foaming. However, it has been found that poor powder properties can be encountered in high-active compositions, for example, powder stickiness leading to agglomeration and poor flow. The higher the desired surfactant content, the less space is available in the formulation for inorganic ingredients, for example builders, to provide porosity and to carry the organic surfactants.
Traditionally, built detergent powder contain a base powder, prepared by spray-drying or non-tower granulation or a combination of such processes, consisting of structured particles containing all, or the major part of, the surfactant and builder in the formulation. Other ingredients that are not suitable for incorporation into the base powder, for example, bleaches, enzymes and perfume, are subsequently admixed with the base powder.
In WO 98 54289A (Unilever) published on Dec. 3, 1998, it has been disclosed that higher total surfactant levels can be achieved without sacrificing powder properties if the traditional base powder is supplemented, or replaced altogether, by separate granular components in which certain ingredients are concentrated or segregated from one another. For example, the powder may be a “modular” one composed of granules containing a high level of anionic surfactant, granules containing a high level of nonionic surfactant, and builder granules containing little or no surfactant.
The anionic surfactant granules disclosed contain from 60 to 99% by weight, preferably from 65 to 96% by weight, of anionic surfactant, for example, linear alkylbenzene sulphonate (LAS). These granules, which are also disclosed in WO 96 06916A, WO 96 06917A, WO 97 32002A and WO 97 32005A (Unilever), are preferably prepared by in-situ neutralisation of LAS acid by sodium carbonate in a flash dryer.
These granules may also be used in formulations which represent a compromise between the traditional and “modular” approaches. WO 98 54287A (Unilever) published on Dec. 3, 1998 discloses laundry detergent powders which comprise a traditional phosphate-built base powder in combination with at least 10 wt % by weight of the high-anionic surfactant granules discussed above.
The anionic surfactant granules disclosed in the earlier filed Unilever patent applications discussed above are of high bulk density, so that they are less suitable for use in lower-bulk-density powders. For handwashing, however, lower-density, more porous products are generally preferred because they dissolve more quickly and completely, which is important when the wash is carried out under conditions of relatively low temperature and low agitation.
It has now been discovered that a similar, wholly or partially “modular” approach may be adopted for powders of lower bulk density, using a different anionic surfactant (linear alkylbenzene sulphonate, LAS) granule having a lower bulk density and a somewhat lower surfactant loading, but still higher than can be obtained using a traditional base powder. This surfactant granule is prepared by a in-situ neutralisation process using a fluidised bed.
WO 94 07990A (Henkel) discloses anionic surfactant granules of high surfactant content prepared using a fluidised bed. The process may involve in-situ neutralisation, for example, primary alcohol sulphate (PAS) paste and a minor amount of LAS acid may be granulated with sodium carbonate on a fluidised bed.
Preparation of detergent base powders containing anionic surfactants (up to 31 wt %) by in-situ neutralisation on a fluidised bed is disclosed in WO 96 04359A (Unilever).
DEFINITION OF THE INVENTION
The present invention provides a particulate laundry detergent composition composed of at least two different granular components, comprising
(a) a granular anionic surfactant component having a bulk density within the range of from 300 to 600 g/l comprising:
(a1) from 40 to 55 wt % of linear alkylbenzene sulphonate (LAS),
(a2) from 45 to 60 wt % of a particulate carrier material comprising
(a21) from 30 to 100 wt % of sodium carbonate,
(a22) optionally from 0 to 70 wt % of finely-divided water-insoluble particulate material,
with the proviso that the carrier material must contain from 25 to 70 wt % of finely-divided water-insoluble particulate material (a22) if the average particle size of the sodium carbonate exceeds 40 &mgr;m, the percentages being based on the carrier material;
(b) at least one other granular detergent component selected from
(b1) a detergent base powder composed of structured particles comprising anionic surfactant, builder, optionally nonionic surfactant and optionally other detergent ingredients,
(b2) a builder granule,
(b3) a granule containing at least 30 wt % of alkyl ether sulphate,
(b4) a granule containing at least 20 wt % of nonionic surfactant.
The invention also provides a process for the preparation of the anionic surfactant granule (a) defined above, which process comprises contacting alkylbenzene sulphonic acid with at least sufficient sodium carbonate to effect neutralisation of the alkylbenzene sulphonic acid, optionally together with a finely-divided water-insoluble particulate material, in a fluidised bed whereby neutralisation and granulation are effected, the amount of alkylbenzene sulphonic acid being sufficient to provide a content of alkylbenzene sulphonate in the granular detergent component obtained thereby of from 40 to 55 wt %.
A further subject of the invention is an anionic surfactant granule (a) as defined previously, prepared by the process defined in the previous paragraph.
DETAILED DESCRIPTION OF THE INVENTION
The detergent composition of the invention is composed of at least two different granular components, one of which is a defined anionic surfactant (LAS) granule. The other may be a base powder, a builder granule, an alkyl ether sulphate granule, or a nonionic surfactant granule. Unless the other granular component is a base powder, the composition is “modular” and preferably comprises at least three different components: for example, as well as the LAS granule, a builder granule and at least one other surfactant granule.
Whether or not “modular”, the composition preferably Contains from 2 to 50 wt % of the LAS granule (a) and from 50 to 98 wt % of other granular components (b), the percentages being based on the total amount of the granular components (a) and (b).
The Anionic Surfactant (LAS) Granule (a)
In the LAS granule (a), the content of LAS ranges from 40 to 55 wt %, preferably from 40 to 50 wt %. The granule has a bulk density within the range of from 300 to 600 g/litre, the 400 to 500 g/litre range being especially preferred. Powder properties and dissolution properties are excellent.
The carrier material, present in an amount of from 45 to 60 wt %, is composed principally of sodium carbonate, but in some circumstances a finely divided water-insoluble particulate material is also present. It has been found that, in order to obtain the desired surfactant loading of at least 40 wt % in combination with good powder properties, it is necessary either to use a finely-divided water-insoluble particulate material to supplement the sodium carbonate, and/or use sodium carbonate that has been milled to a smaller than normal average particle size.
If the sodium carbonate has an average particle size not exceeding 40 &mgr;m, then the presence of finely-divided water-insoluble particulate material is not necessary; but may in any case be desirable. Sodium carbonate milled to an average particle size within the range o
Groot Andreas Theodorus Johannes
Klaver Marco
Mitelman Rimma
Ogden Necholus
Unilever Home & Personal Care USA , division of Conopco, Inc.
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